1. Field of the Invention
The invention relates to a coating system comprised of a resin component, a hardener component, and additives, and its use in the preparation of laminated pressed plates with a surface coating consisting essentially of polyurethane acrylates.
2. Description of the Related Art
The use of laminated pressed plates for indoor and outdoor applications in the construction sector is known, where the surface of the plates must meet high requirements with regard to mechanical properties such as surface hardness and scratch resistance. In the case of laminated pressed plates for outdoor applications, high requirements are also imposed regarding resistance to UV radiation and weathering.
According to EP-A-166653, a laminated pressed plate with improved scratch resistance, namely at least 2 newtons, is provided which has on the surface of its plates an acrylic resin layer that has been cured by radiation. To manufacture these plates, the outermost web of the carrier material, e.g., a web of printed decorative paper, is coated on one side with polymerizable acrylic resins so that a solid resin film is created. Then this film is exposed at room temperature to electron beams, causing a radical cross-linking reaction to occur. Finally, this cross-linked acrylic resin film forming the outermost layer is pressed at high pressure and temperature in a pressing stack of the type customarily used for laminated pressed plates.
This method is tedious from the standpoint of machine technology inasmuch as an electron radiation source with a relatively complicated type of construction is required in order to achieve the desired surface hardness of the acrylic resin layer.
In addition, the cross-linked acrylic resin film is difficult to manipulate in discontinuous pressing processes inasmuch as it tends to curl easily and not lie flat when the pressing stack is being loaded in layers. This effect is based on a radiation polymerization induced high acrylate cross-linking density, which is in turn associated with material shrinkage of the acrylate polymers.
The invention is intended to remedy this problem.